Still Running Rich... what now??

I've got a Peugeot 103, all stock. I de-restricted my exhaust, took off the air box and cleaned my gurtner carb, which was pretty clean already when I took it out but I blasted some carb cleaner in there and used some compressed air afterwards.

All this stuff helped a little but I still 4-stroke from 18mph on up to the max of 25mph. If i cut the fuel while riding I blast up to 30mph.

I think I need to downjet but I don't know what my stock jet size is, how can you tell? Also, the only place I've found to get gurtner jets is mopedshop.com and they only stock 60 and 62.

anyone have a recommendation?

Re: Still Running Rich... what now??

no air filter and still four strokes? tough one. is that the stock carb? can u rig up a different carb easily?

Re: Still Running Rich... what now??

I'd have to get a new intake I think. Not super easily. But can Gurtnet jets be found anywhere? Should I avoid downjetting?

Re: Still Running Rich... what now??

did you derestrict your exhaust too much?

Re: Still Running Rich... what now??

Put a delorto on there dont mess with that gurtner crap...make sure timing is correct...I have found that advancing timing a little more than stock is better performance overall ...if you must stay with gurtner you can use micro drill bits to get a measurement ...even a 12/14 delorto works better than a gurtner. find a cable choke one to retain handle bar control..that ped should cruise 30-35...

Re: Still Running Rich... what now??

15.15's require a new intake I believe. How do i get the intake off on a 103? can i take the variator spring out to unscrew the intake? Will that spring go back on easily? that photo's what i'm talking about.

1204532740_spring.jpg

Re: Still Running Rich... what now??

float might be set too high

Re: Still Running Rich... what now??

Float? You mean the floatbowl? I took my carb apart and I don't think it can be set at all.

Re: Still Running Rich... what now??

It's possible that it's actually running too lean with all of that work you've done. Lean four stroking sounds very similar to rich four stroking. Throw a new spark plug on there, take it for a wide open throttle run and check the plug color.

Re: Still Running Rich... what now??

I doubt I'm running lean. When I turn the gas line to the 'off' position at full-throttle I get a burst of speed as the gas runs out. Also, it occasionally will break out of the 4-stroke to the higher-pitched more powerful sound.. but that only started after I de-restricted the exhaust and removed the air box.

I've got a #54 jet on the way from handybikes (down from a #60) so we'll see what happens then.

Re: Still Running Rich... what now??

Two things: the float is stuck and the carb is pouring gas out OR the engine has very little compression left and just cant burn all the gas (so when you cut the fuel you get a burst of speed when it can handle the gas)

Re: Still Running Rich... what now??

The carb isn't pouring gas. I've taken it apart, all the seals are good and it's clean as a whistle. As far as the engine being bad, I've taken the piston cylinder off and cleaned it out and lubricated, everything should be fine in the engine. Is there something else that could be wrong with it leading to low compression?

Re: Still Running Rich... what now??

Well, bad piston rings would do it, they may not look bad when you took them off but can still be. Also, not sure if your ped comes with a decompressor, but that valve not closing all the way or having a bad seal would give you bad compression...

Re: Still Running Rich... what now??

Hmmm. The piston rings are "new," I broke the old ones when I messed with it before so I got some from mopedjunkyard. Do you think they might be bad? How do I fix the seal on the decompressor valve? Do I have to get a new head?

Re: Still Running Rich... what now??

I could be wrong, your problem may be something else. I would do a compression test on the motor, take it to a local autoparts store and they will do it for free if you dont have a gauge. If the compression is ok its something else. If the comp is bad and the rings are new, then its most likely the valve, there are a few ways to seal those. I would then take the head off and check the valve. Best way for me was to aim the head at a very bring light and see if any light comes through around the decomp valve on the other side. If it does its not sealing. Then you take the valve off and see if its the valve or the head thats damaged. If its the valve, get a new one. If its the head, you can get a buildup material and make a new seal (same stuff used on valve jobs in a car). Sometimes you can just adjust the tension and it will seal. But check the compression first, so you dont end up doing a bunch of empty work...

Re: Still Running Rich... what now??

I don't know jack about the internal combustion engine, this moped is my first introduction, although I have taken apart my chamber and milled around in the piston and what not. What is a valve?

Re: Still Running Rich... what now??

wait, maybe you mean the hole that opens when you pull the decompressor?

Re: Still Running Rich... what now??

Well the hole is where the valve sits. The valve is the thing that closes the hole. On 4 stroke engines valves open and close to let air in and exhaust out, but on a 2 stroke you only have the decomp. If it doesnt sit well air will leak around it and cause a huge loss in compression. As far as piston rings go: you will have one or two rings depending on moped/kit. Over time the rings get slowly ground down due to friction with the cylinder. Its a very tiny difference, you probably would not even notice it unless you had a worn and a new piston ring side by side. But, once the rings get small enough the compression drop becomes very large. Many mopeds will still run, but have low power and other weird symptoms. I have even heard of them gaining power for a little while!!! I also didnt realize that your stock carb has a removable jet, always thought Gcarb was not tunable. Double check before you go and buy jets. If anyone did change the jet on it, that could very well be your problem as well. Do a comp test , if comp is good do a spark test (pull the plug out, touch it to the cylinder and crank the engine, you should see a strong spark). If the compression and the spark are both good, it must be a fuel problem...

Re: Still Running Rich... what now??

Got it, I'll check for valve leaks and go for a comp test. I bought the rings from moped junkyard, so there is a slight possibility I've been ripped off, but I'll try new rings last to avoid spending too much money.

I'll do a plug chop too. I replaced the plug in January and by February it was carbon fouled, although after taking everything apart the carb and engine were really clean so perhaps it was just fouled from running rich?

Gurtners have removable jets. I bought a #54 (down from a #60), hope that's not too lean. Everyone talks shit about them but mine is probably 15 years old and it was clean as a whistle when I took it apart. I also didn't see all those tiny little holes that fill up with stuff like everyone says. Maybe the Motobecane Gurtners (which are a different design) are less forgiving.

Thanks so much for all the advice!

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